Census and hospital discharge data from Sweden and Denmark and U.S. Veterans hospitals, linked for follow-up to cancer, mortality, and population registries where available, were used to assess cancer risk among individuals with specific medical and occupational exposures. Mortality among diabetics in Sweden was elevated for all major causes of death, particularly circulatory, respiratory, digestive, genito-urinary, and malignancies. The youngest diabetics had the greatest increased mortality from all causes. Obese Swedish patients were at increased risk of cancers of the digestive tract, urinary tract, female reproductive organs and connective tissue. Swedish patients with hemochromatosis had a cumulative risk of hepatic cancer of 10% after about nine years. Swedish Celiac patients had an increased risk of lymphoma and cancers of the upper digestive tract.I n Danish and U.S. Veterans hospital data, we investigated the link between inflammatory bowel diseases (ulcerative colitis and Crohn's disease), appendectomy and cancer. We found no evidence of a reduced risk of ulcerative colitis subsequent to appendectomy in either Danish patients or U.S. veterans. In contrast to patients with ulcerative colitis, Crohn's disease patients were at increased risk of cancers of the small intestine, but not colorectal cancers. Danish women with molar pregnancy were not found to be at increased risk of any cancer other than gestational choriocarcinoma. Danish women hospitalized with gonorrhea were at increased risk of cervical pre-neoplasia, but not invasive cervical cancer or any other cancers. Danish women with anorexia nervosa had a non-significantly reduced risk of subsequent cancer, which is consistent with the theory that energy restriction may decrease tumor development. Swedish men and women employed in occupations exposed to diesel engine emissions showed increased risks of respiratory and digestive cancers, and also cervical cancer among women. Butchers and other meat workers were also at increased risk of respiratory and digestive cancers. A study of Swedish construction workers found that even small excesses in weight or blood pressure were associated with increased risk of renal cell cancer, and reduction in blood pressure was associated with reduced cancer risk. A large new study was initiated this year to assess familial aggregation of autoimmune diseases and lymphoproliferative malignancies (LP). We will study 50,000 Swedish and 10,000 Danish cases of LP, a similar number of non-cancer controls, and all their relatives' computerized medical data (cancers and hospital diagnoses).